Japan's Prime Minister Yukio Hatoyama listens to questions during a press conference about the relocation of U.S. Marine base in Okinawa, at his official residence in Tokyo, Friday, May 28, 2010. Hatoyama said that the government had investigated 40 sites as alternatives for Futenma, including options off the island, but none worked. He said Futenma's helicopter and air assets needed to nearby Marine infantry units based on the island in times of emergency - reminding listeners that recent events on the Korean peninsula had made the region "extremely tense." (AP Photo/Junji Kurokawa)
(Junji Kurokawa - AP)

TOKYO -- Japan's increasingly unloved prime minister was battered Sunday with more demoralizing news, as a small political party abandoned his ruling coalition ahead of a key election and a poll showed that more than half the electorate wants him to quit.

Less than a year ago, Yukio Hatoyama garnered a landslide election victory that ended nearly a half-century of one-party rule. His Democratic Party of Japan (DPJ) seemed then to have a historic mandate to revive the country's stagnant economy and reform the government's sclerotic bureaucracy.

But Hatoyama has since shown an astonishing capacity for indecision. His government frittered away most of the past nine months trying to decide whether and where the U.S. Marine Corps would be able to relocate an air base on the island of Okinawa.

Finally, he decided Friday to renege on a campaign pledge to move the noisy base off the island. Acceding to U.S. pressure, he agreed to uphold a previous government's commitment to keep the Marines on Okinawa, albeit at a less populous location.

His long-delayed decision -- which is wildly unpopular on Okinawa -- triggered Sunday's move by the tiny Social Democratic Party to leave the ruling coalition.

The defection does not force the DPJ from power, as the party still holds a commanding majority in the powerful lower house of parliament. But it may lessen the ability of Hatoyama's party to secure a majority in upper house elections in July -- and it could limit his capacity to pass laws.

"As the Social Democratic Party, we want to keep the promises we make to the people," the party's leader, Mizuho Fukushima, told reporters Sunday.

Hatoyama had fired Fukushima from his cabinet on Friday after she declined to support the Okinawa base relocation deal.

For voters across Japan, the Okinawa issue is emblematic of Hatoyama's seeming inability to make up his mind in a timely way on a broad range of issues and campaign promises. He has waffled on pledges to abolish highway tolls and pay cash allowances to encourage parenthood.

Public support for his government has fallen to a new low of 17 percent, according to a poll released Monday by the Asahi newspaper. A weekend poll by the Kyodo news agency found that 51 percent of those surveyed think he should resign over his failure to solve the base issue as he had promised he would.

In a striking measure of the political damage caused by Hatoyama's indecisiveness, the Kyodo poll found that the DPJ is now less popular than the long-ruling party it defeated in elections in August.

Some members of his party have begun to whisper that he should quit. There would be little time, however, for a new leader to pull together a campaign for the upper house vote on July 11.